Subtractive process for color photography



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WIIIVA fran t aida 'rinse HIS ATTORNEYS Patented Apr'. 2, 1940 UNITED STATES I PATENT OFFICE lanntoss sunrnao'nvE rnoorzss Foa ooLon PHOTOGRAPHY Eugene G. Scary, Binghamton, N. Y., assignor, by mesne assignments, to General Aniline Film Corporation, New York, poration of Delaware N. Y., a cor- Application March 31, 1938, Serial No. 199,093

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ducing multi-color partpictures involves the exposure of a multi-pack in an ordinary camera to simultaneously produce vblack and white colorseparation latent images. The separation images are then converted into proper dye images by a controlled diusion development. In this controlled diffusion method, chemical agents are permitted to diffuse to a limited extent into the tripack to effect the changes desired. As is evident,

the thickness of the layers of the tri-pack is quite small and as a result this process, to give proper color rendition, requires the exercise of the greatest care and skill. In fact such skill is necessary that. it is impossible for anyone other than the laboratories actively engaged in the processing work to convert the latent images into multi-color pictures. It is also manifest that in view of the care required the cost of processing is relatively high. This method is, therefore, open to objection for these reasons.

It is known that silver halides, i. e. the chloride, iodide and bromideLdiier considerably as regards their solubility in ammoniacal solutions. Thus silver chloride is the most soluble of the three,

being about twenty times as soluble as silver bromide. Silver iodide, on the other hand, is the least soluble of the three, being only about one hundredth as soluble as silver bromide. By taking advantage of these diierences in solubility of these Asilver halides, I have devised a process for producing colored prints and' transparencies which avoids the objections which manifest themselves in the processY previously mentioned. My process involves the utilization of a multi-pack in which the emulsions of at least two of the layers contain a different silver halide.- Thus the light-sensitive vmaterial may be a tri-pack with a layer of vsilver chloride, a. layer of silver bromide and a layer of silver iodide, a tri-pack with two layers of silver bromide and one of silver iodide, a bi-pack with a layer of silver bromide and one l of silver iodide, and the like. After exposure, the

ing emulsion layers of dierent silver halides, is,l` I

employed.

It is a further object of my invention to provideva process involving the use'of soluble ferrocyanides in ammoniacal solutions of diierent concentrations in treating an exposed light-sensitive material having layers containing different silver halides.

It is a further object of my invention to provide a process for forming multi-color part pictures in which it is unnecessary to carefully con-- trol the degree of diffusion of the processing agents into the light-sensitive material.

. A further object of my invention involves a light-sensitive material in the form -of a multipack in which at least two of the layers contain different silver halides.

Other important objects will be seen-from the detailed description following hereafter.

As previously stated, my process relies for its eflicacy upon the utilization of a multi-pack which may have a base of paper, cellulose nitrate, cellulose acetate or the like, in which at least'two layers carry a different silver halide gelatin emulsion. 'Ihe particular manner of compounding the light-sensitive material from the standpoint of arranging the layers on the base and of arranging the order of the different halide layers, may be I varied to a considerable extent. For instance all three layers may be positioned on one side of the The vyellow and blue color is imparted to the proper layers by means of inorganic pigments. Forv this purpose I prefer the ferrocyanldes which are formed in situ during the processing of the nlm. Thus Ierric ferrocyanide may be used for producing the blue color and vanadium ferrocyanide for producing the yellow color. It is also possible to produce the red color by means of a ferrocyanide pigment such as uranium ferrocyanide. Similarly nickel di-methyl glyoxime may be used for this purpose. However, due to the lack of brilliance of the red pigments, it is advisable for best results to produce the red color by the process known as color development. -A discussion of color development may be found on pages 404-407 of History of Three-Color Photography by Wall. On ypage 406, compounds As is usual in color photography, my multipacks, especially in those layers designed to Vregister the red and green color sensations of the object, are sensitized to eect color separation in said layers. Dyestuifs suitable for this purpose are well known in the art, a list of such dyes being given, for instance, on pages 252-263 of "History oi Three-Color Photography by Wall. I prefer, in forming my multi-packs, to sensitize forthered region with Pinacyanol and for the green region with Eosln.

The facility with which my process may be vaccomplished may be perceived by considering its application in its general aspects to, for example, a light-sensitive material having a gelatino-silver chloride 1ayer,.sensitized to red, positioned` on a base, a gelatino silver iodide emulsion layer sensitized to green positioned on said first layer, land a gelatino-silver bromide emulsion layer not specially sensitized, positioned on said second layer. Said light-sensitive material is exposed and developed in the ordinary way after which it is subjected to the action of white light. The developer employed may be any developer. Should silver chloride be present in one of the emulsion layers, the'developer should in additionbe free from bromide. 'I'he light-sensitive material is now subjected to the action of a weak ammoniacal solution containing a soluble ferrocyanide, i. e. an alkali-metal ferrocyanide, the

strength of said solution being such that, while it will dissolve silver chloride. it has no effect upon silver iodide or bromide. Silver ferrocyanide is produced in the silver chloride layer by this treatment as a result of the dissolution of the silver chloride by the ammonia and its reaction with said iferrocyanide.` The silver ferrocyanideis then converted to ferrie ferrocyanide by an acid treatment with ferrie chloride.v 'I'he silver bromide layer is now colored by means of vanadium ferrocyanide by dissolving the silver bromide with a stronger ammoniacal solution than that used in the ilrst treatment, said solution also containing an alkali metal ferrocyanide, the silver ferrocyanide thus obtained being converted to vanadium ferrocyanide by an acid treatment with vanadium chloride. A silver and dye image is next formed in the silver iodide layer by development in a paraphenylene diamine developer containing a color component which is capable of reacting with the oxidation product of the'developer to produce a dye imparting a reddish color.

Fig. 2 the processing of a film.

Example 1.-The tri-pack of Fig. 1 comprises a paper support I upon which is superimposed a red sensitized silver chloride gelatin emulsion 2, a green sensitive silver iodide gelatin emulsion 3 and a non-sensitized silver bromide gelatin emulsion 4. The latter emulsion contains an agent for imparting a yellow. color to the emulsion for the purpose of preventing blue light from passing to the green and red sensitive emulsion layers. It desired, the same result may be obtained by interposing a yellow dye layer between layers 3 and 4. For this purpose tartrazine which is discharged during development has been employed although it is to be borne in mind thatother dyestuil's usually employed in the art for this purpose may be utilized. 'Ihe paper is exposed either directly or through iilters to the action of light, whereupon there is produced in the lowermost layer a latent image of the red sensations of the object,

in the intermediate layer a latent image of the green sensations of the object and in theouter most layer a latent image of the blue sensations of the object. The paper is next developed in a bromideless developer such as amidol, rinsed, and subjected to the action of white light. After the exposure the silver chloride emulsion layer is treated for about 5 minutes in a .1 to .5% solution 'of ammonia containing added potassium ferrocyanide. Dissolution of the silver chloride takes place with the immediate precipitation of silver ferrocyanide through reaction of the dissolved chloride with the added potassium ferrocyanide. A washing in water is interpolated between this step and the succeeding step wherein the paper is subjected for a short time, say, about 3 minutes, to the action of a solution containing about 2% of ferric chloride acidiiled with hydrochloric` acid. A reaction ensues between the silver ferrocyanide and the iron chloride resulting in the formation of ferrie ferrocyanide, silver chloride being regenerated. The silver chloride is removed by a treatment in a dilute ammoniacal solution, a treatment for about 5 minutes in a 1% ammonia solution being eiilcacious in accomplishtime, say about 5 minutes with a stronger ammoniaca] solution than that previously used. Preferably a 5% solution is employed at this stage. 'Ihe ammoniaca] solution contains potassium ferrocyanide which reacts with the silver bromide to produce silver ferrocyanide. Following a rinsing step, the ferric hydroxide in the lowermost layer 2 is reconverted' to ferrie ferrocyanide by means of an acid potassium ferrocyanide bath. After washing for a short time, the paper is next treated for about three minutes in a 2% vanadium chloride solution containing free hydrochloric acid. Vanadium ferrocyanide, a light yellow compound, is thus produced in the outermost layer. The silver chloride produced as a by-product in this reaction is removed by a treatment with 5% ammonia solution, whereby the ferrocyanides of iron and vanadium are converted to their respective hydroxides. After rinsing, the paper is then subjected to the action of a p-phenylenediamine developer containing methyl phenyl pyrazolone. The products of oxidation produced by the reduction oi' the silver iodide in the intermediate layer thereupon react with the methyl phenyl pyrazolone to produce a ings, as there depicted, involves a departure fromA the paper of Fig. -1 in the arrangement and nature of the emulsion layers. In this modiilcation vthe lm base I has arranged on the entrant side of the( illm a silver bromide emulsion layer 2 containing al yellow dyestufl such as tartrazine. On the opposite side of said lm base there are llocated two emulsion layers 3 and 4, layer 3 being a silver iodide emulsion sensitized for green, and layer 4 being a silver bromide emulsion sensitized for red. Ihe light-sensitive material, after exposure, if desired behind filters, is developed in an amidol developer to produce white and black color-separation images. The iilm,

after exposure to white light, is treated with a 5% ammoniacal solution containing about 5% potassium ferrocyanide, as a' resultfoi which the silver bromide in layers 2 and 4 is converted to silver ferrocyanide. After Washing, layer' 4 alone is subjected to the action of a 2% 'ferric chloride solution acidifled with hydrochloric acid. In this way the silver ferrocyanide in layer 4 is converted into ferric ferrocyanide. 'I'he next step involves the treatment of layer I with a 2% vanadium chloride solution, acidified with hydrochlorc acid to convert the silver ferrocyanide of this 'layer into vanadium ferrocyanide. The silver chloride which is produced in forming the ferric and vanadium ferrocyanides respectively, is removed with a, say about 5% ammonia solution subsequent to a washing of the film. In this removal of the silver chloride, the ferrocyanides oi iron and vanadium are converted to ferrie hydroxide and vanadium hydroxide respectively. The silver iodide layer 3 is now developed with a paraphenylene diamine developer containing methyl phenyl pyrazolone whereby the oxidation products 'of the diamine combine with the methyl phenyl pyrazolone to produce in this layer a silver and dye image. The film, following a rinsing operation, is subjected to the action of an acidifled potassium ferrocyanide solution to cause regeneration of vanadium and ferrie ferrocyanides from their respective hydroxides. chromio acid, a transparency having yellow, magenta and blue dye images is obtained. The same or .similar procedure may be adopted in processing a illm having 2 silver chlorideand one silver iodideor one silver bromide-emulsions.

In referring to the solutions by which the silver salts are dissolved, Ihave typified the same as ammoniacal solutions.` This term is to be construed as covering not only solutions of ammonia but in addition solutions oi' ammonium salts as well as solutions of amines. Examples of the ammonium saltsI are ammonium sulfate, ammonium acetate, ammonium chloride and the like. Examples of the amines vare the alkylol amines such as ethanol amine, di-ethanol amine, tri-ethanol amine, propanol amine and the like, alkyl amines such as methyl amine, ethyl amine,

propyl amine and the like, hydroxyl amines, etc.VV

It is to be pointed out that for the purposes o! my invention the ammonium salts and the By now bleaching out the silver with y 3 amines function to produce the result desired although I prefer solutions oi' ammonia.

In the preceding examples, in lieu of removing the silver chloride by means of ammonium hydroxide at the times indicated, I also contemy plate converting the ferrie and vanadium ferrocyanides to their respective hydroxides by means of a dilute alkali such as sodium hydroxide, potassium hydroxide and the like, after which the silver chloride may be removed by dilute aml monia such as that having a concentration of It should be understood that thisl and other modications apparent to a person skilled in the art are within the scope of my invention. Thus instead of using separate layers 'of different silver halide emulsions, I may em- .ploy a single layer in which the different silver halide emulsions are present in admixture with each other.

What I 4claim is:

l. InA the process of `producing multi-color pictures in which latent images are formed in a multi-layer gelatino-silver halide light-sensitive material in which the emulsion of one layer of material to the action of a soluble ferrocyanide in an ammoniacal solution of such strength that only one of the silver halides is dissolved and converted into silver ierrocyanideby the soluble ferrocyanide present. j

2. In the process of producing multi-color pictures in .which latent images are formed in a gelatina-silver halide light-sensitive material having three layers, the emulsion of one of said layers being formed with a silver halide different from the silver halide used to form the emulsion of at least one other layer and in which the latent images are then developed in a black and white developer but not xed, the improvement which comprises re-exposing the light-sensitive material kto white "light, subjecting the light-sensitive material to the action of a soluble `ferrocyanide in an ammoniacal solution of such strength that o nly one of said silver halides is dissolved and converted into silver ferrocyanide by the ferrocyanide present, and subjecting the light-sensitive material to the action of a soluble ferrocyanide in an ammoniacal solution of such strength that only one other of said silver halides is dissolved land converted into silver ferrocyanide by the ferrocyanide present.

3. In the process 'of producing multi-color.

pictures in which latent images are formed in a f gelatine-silver halide light-sensitive material having three layers, the emulsion of one of said layers being formed with a silver halide different from the silver halide used to form the emulsion of at least one other layer and in which the latent images are then developed in a black and white developer but not xed, the improvement ferrocyanide into ierric ferrocyanide and then 7';

subjecting the light-sensitive material to the action of a soluble ferrocyanide in an ammoniacal solution of such strength that only one other o! said silver halides is dissolved and converted into silver ferrocyanide by the ferrocyanide present.

4. The process of' producing multi-color pictures which comprises exposing a multi-layer gelatino-silver halide light-sensitive material, in

which the emulsion of one layer being formedwith a silver halide different from the silver halide usedto form the emulsion of another layer,

I in the silver ferrocyanides inthe separate layers are converted into ferric ferrocyanide and vanadium ferrocyanide and wherein a silver and dyestuif picture is produced in the third layer by color development.

'1. The process of producing multi-color pictures by exposing a tripack in which at least one oi' the layers is a silver bromide emulsion and another of the layers is a silver iodide emulsion, developing the latent images in a black and white developer and without xing, converting the silver bromide into silver ferrocyanide by an ammoniacal solution containing potassium ferrocyanide to which the silver iodide is inert, treating the light-sensitive material with a chloride selected from the class consisting of iron and vanadium to convert the silver ferrocyanide into a ferrocyanide selected from the class consist ing lof iron and vanadium, removing silver chloride by means oi' an ammoniacal solution having no dissolving power on silver iodide, producing a silver and dyestuff image in the silver iodide layer by color development, reconvertlng the metal hydroxide formed in the silver chloride removal step to the corresponding ferrocyanide by acidied potassium ferrocyanide and removing metallic silver. f

8. The process as defined in claim 1, in which the ammoniacal solution is a solution oi an ammonium salt.

9. Theprocess as denned in claim 1, wherein the ammoniacal solution is a. solution of an amine.,

. EUGENE G. BEARY. 

